1. Field of the Invention
The present invention relates to a thick film capacitor.
2. Description of the Prior Art
A thick film capacitor has a structure wherein a sintered layer of ferroelectric materials is sandwiched between metal electrodes. Ferroelectric compounds used for the thick film capacitor normally have a poor degree of sintering, and it is very difficult to constitute a sintered layer solely by the ferroelectric compounds. For this reason, in the conventional thick film capacitor, a crystalline or amorphous glass is added as a binder to perform sintering, thereby forming the sintered layer of the ferroelectric materials.
However, the addition of glass remarkably degrades the dielectric characteristic of the sintered layer of ferroelectric materials. For example, when a commercially available crystalline or amorphous glass is added to ferroelectric inorganic compounds having a dielectric constant of 20,000 and the mixture is sintered, the dielectric constant of the resultant sintered layer of ferroelectric materials is considerably degraded to 100 to 1000, i.e., a value 1/20 to 1/200 the value before sintering. This is because, upon sintering with a glass additive, the perovskite structure of the ferroelectric inorganic compounds is destroyed.
Since the conventional thick film capacitor contains glass in the sintered layer of ferroelectric materials, it has poor moisture resistance. The conventional capacitor easily causes migration of electrode metals, i.e., has a poor migration resistance.